1. Technical Field
The present invention relates generally to video surveillance and more specifically to a method for evaluating entrants to a secured area for abnormal activity.
2. Description of the Prior Art
Security systems using video cameras are well-known in the art, and have been used extensively for decades. Such surveillance, however, is expensive, for while an automated system can easily record images, interpretation of these images is significantly more complex. It is thus necessary to have the output of the cameras reviewed by a human operator to detect abnormal situations. Where this manpower is unavailable, video footage has been useful mainly for investigation of a prior incident or for deterrence purposes.
As digital processing techniques have improved, other techniques have attempted to alleviate this need for human intervention. For example, a number of motion detection systems have been developed, requiring an operator to review only those images that show motion. This system can be useful for surveillance of a home or other areas with a relatively stable environment. A system relying on motion, however, suffers from a high frequency of false alarms. Events as trivial as the passage of animals through the monitored location or objects moved by a gust of wind can result in detected motion even when no abnormal condition exists.
Further, a motion detection system is ineffective in areas where the environment is not stable, where motion is common. One such location is a public building or park. In these areas, an operator is not interested in detecting every entrant to the area, but only those who may represent some threat to the area's security. It would be desirable to pre-evaluate entrants to a secured area to concentrate the attention of a human monitor on those entrants most likely to pose a threat to security.